Pressure atomizing oil burner



Nov. 12, 1946. A, LOGAN rnassums A'roMIzmG OIL BURNER 2 Sheets-Sheet 1Filed Oct. 4, 1944 mvsmon J 1.506115 Bu VUTTORNEYS Nov. 12, 1946.

J.'A. LOGAN 2,411,048

PRESSURE ATOMIZING OIL BURNER Filed Oct. 4. i944 2 Sheets-Sheet 2INVINTOR MLOGHN *HTTORNEYS I Patented Nov. 12, 1946 PRESSURE ATDRHZINGOIL BURNER Joseph A. Logan, Hadley, Mass, asslgnor to Gilbert & BarkerManufacturing Company, West Springfield, Mass., a corporation ofMassachusetts Application October 4, 1944, Serial No. 557,119

2 Claims. (Cl. 158-28) This invention relates to a new structure andmode of operation in gun type oil-burners. The gun type burner is wellknown. It operates to pump oil under pressure through an atomizingnozzle, mix the spray with air supplied under pressure from a fan and toignite and burn the carburetted air.

In the prior art much attention has been given to the emciency of theatomizing nozzle. An account of this is published in the Transactions ofthe A. S. M. E. of July 1939 under the title "Atomization of oil bysmall pressure atomizing nozzles. Reference to this publication willgive a background to what is said about nozzles in disclosing thisinvention.

A main purpose of the invention is to provide a new gun type structureto burn oil from a relatively large nozzle at a low rate in the amountper hour. It is most useful in serving small heaters for domestic houseand hot water heating.

In referring to the prior art, gun type burners are being considered.These are oil pressure atomizing burners.

Ordinarily the oil burning rate per hour is determined by the size ofthe atomizing nozzle. The small ratein present practice calls for acorresponding small nozzle size. Ordinarily the rate is not changed muchin practice by changing the pressure for feeding oil to the nozzle. Thatpressure is commonly adjusted or determined in practice by what willgive the most eilicient kind of a nozzle spray; any change of 2 providefor using in the new structure a practical dependable nozzle, sized togive a rate of one gallon an hour when used in the practice with priorart burner structures. The new structure will operate successfully withthis nozzle at a rate substantially less than one gallon an hour, forexample a rate of about one-half gallon an hour. The same structure willalso operate successfully at the normal rate of one gallon per hour whensuch larger rate is .wanted. Thus a substantial range of burner rates.is available rate due to oil pressure being incidental to that purposeof efficient spraying. All this is indicated in the above publication.It is seen that the rate is made primarily by the size of nozzle. And itis seen that'the lowest rated nozzle of that published investigation isone gallon an hour. I know nozzles have been made for smaller rates thanone gallon. But I known that as the nozzle sizes go below the sizeintended for one gallon, the expense of making them accurately for adesired smaller rate increases and there is a practical limit. There isanother practical limit caused by the increasing liability of very smallnozzles to clog up in use. The size for the one gallon rate has anorifice in the neighborhood of one hundredth of an inch in diameter.

According to one feature of my invention I provide for using a nozzlewhich would be altogether too large for the desired rate under thecommon practice and compensate for the oversize by cooperating structureto get the desired Y low rate when wanted. By way of example I which ismost useful in providing for the lower rates.

An example of specific structure for embodying the principles of theinvention will be understood frcm the accompanying drawings, thedescription and mode of operation to be disclosed in the description.

Referring to the drawings:

Fig. 1 is a side and Fig. 2 is a rear view of the new gun type burner topractice the invention; these views showing the casing partly brokenaway with some detail appearing in the assembled form;

Fig. 3 is a view looking at the front of the burner head of Fig. l butwith an added element;

Fig. 4 is a sectional view on line 5-5 of Fig. 5, of a centrifugalclutch also seen assembled in side view. with other burner parts in Fig.2;

Fig. 5 is a face view with an end plate removed, of the clutch of Fig. 4showing one way of adjusting it for a range of timing operations;

Fig. 6 is a sectional view of a conventional atomizing nozzle such asused in gun type burners, the scale being enlarged considerably in thedrawing of this element; and

Fig. 7 is a sectional view of a conventional oil pump by-pass such asused in gun type burners, the view is taken on a horizontal planethrough the pump output of Fig. 2, some oil passages not particularlypertinent here being omitted.

The burner assembly of Figs. 1 and 2 has a casing i for a multi-vane fan2 to drive air into cylinder 3. The fan is driven by direct shaftconnection with motor 4. The motor has a shaft transmission to oil pump5. In this transmission there is a centrifugal clutch 5 and acoupling 1. A transformer 8, electrical conduit 9 and stand IB areindicated and need no description.

The oil discharge conduit ll leads from the pump 5 -to an atomizingnozzle l2. The oil is atomized by the pressure of the oil through anozzle structurelike that of Fig. 6. The nozzle is positioned axially ofcylinder 3. It .may be screwed on the end of pipe 1 I, the latter beingheld by a member I3. As shown the member is a closure at the. rear endof a perforated cylinder H for which it serves as a support at that end,see Figs. 1 and 3. A spider held by screws through cylinder 3 supports.the member 13. Electrodes l5 pass through the member I3 with spark gapterminals adjacent the orifice of the atomizing nozzle. The member l3may have as shown in Fig. 3, two air feed openings l6 through it. Theseopenings are not large. They serve with sliding covers, merelyindicated, to let a supplementary air supply .go through the member 13when wanted and be completely closed when such supply is not wanted inany particular instance.

The perforated cylinder l4 provides a combustion chamber B. It is acylinder having many perforations through which air is fed to meet theatomized oil spray. The air comes from the annular space A, the cylinderserving as a jacket around cylinder M to provide space A. The air fanwill establish air pressure in jacket space A .and the air will feed tospace B in a great many air pressure jets or streams. The front end ofspaceB is open. The frontend of space A is shown closed by the spacingring indicated there while therear end is open as the annular spacebetween member l3 and cylinder3 is open, except for'the spider supportbefore mentioned. The purpose of the small shuttered openings it throughmember 13 is to adjust for a small supplementary air supply. .much lessthan the amount of air fed through the perforations in cylinder M. Thesupple- Thelatter is always mentary supply should never be enough tochange the dominant character of the radially moving air, forced throughsaid perforations. The jacket receives substantially all the air fansupply, but

this statement is to be understood as not excluding a minorsupplementarysupply through openings I6 directed parallel to the oilsupply. One idea in the supplemental air supply is to have it meet theoil spray from the rear and break it up. For, example at less thanthebest oil pres-- sure for the best atomizing result per se, an operationinvolved in this" invention to beexplained, the tendency is for the oilspray to take a cup rather than a coneform. The supplemental air supplyis directed at the cup form from the rear, breaks it up into a bettercondition to get mixed with the radially directed air .jets from the airjacket. The supplemental air supply is also useful in locating, to someextent, the point where the flame begins. The air supply radiallydirected from the air jacket, however, is always enough greater than thesupplemental when the motor shaft l1 turns. The latter is fast tothe'motor armature and the fan always turns with the armature. When themotor is switched off its armature having considerable momentum willturn the fan and the action is a gradual stopping of the -fan after themotor current is cut off.

On the hub l9, Figs. 4 and 5, three clutch driving shoes are mounted asindicated. These are driven by pins 2! carried by the hub. Each shoe ismade of two parts 22 and 23. A separate screw 24 is threaded througheach part 23. It has a counters'eat for its head the outer face of part'23. Itiwill be seen from Fig. 5, that with this construction, the parts22 and 23 of each similar shoe can be held apart by adjusting screw 24.A pair of tensioned coil springs 25, each one arranged as a full ring inone of the opposite side face recesses, will tend to pull the parts 22and 23 of the shoes together. But screws 24 will determine stoppingpoints. When screws 24 are turned with tendency to go inwardly, parts 23must move outwardly as the screw ends are always held against parts 22by the springs. Such outward movement of shoe parts 24 will increase thetension of springs 25. When shaft l1 speeds up the tension of springs 25will determine at what time or at what speed the mass of shoe parts 22and-23 will be centrifugally moved out for the parts 23 to engage thedriven part of the clutch.

The driven clutch part consists in the drum 26 fast on hub 21. Thelatter is mounted for free running on hub l9. It is held against comingoff axially by the head of shaft screw 18. This screw I head is arrangedin a recess, see Fig. 4, so it will not have any effective frictionalcontact tending to drive the driven part of the clutch. What frictionoccurs will tend to keep the screw in place. its having a threaddirection for that purpose. This recess for thus pocketing the head ofscrew 68, is closed by a plate fastened to hub 21 to rotate with thelatter. Suchplateis part of the connector end 2'fforming a part to joinwith the flexible shaft coupling 1' indicated in Fig. 2. This couplingpositively connects the shaft of the oil pump 5 with the driven half ofthe centrifugal clutch above described. The result is that the motor isprovided with a transmission to always drive the fan with its armatureand a centrifugal clutch in the transmission to drive the oil pump onlywhen the fan is at a desired supply to dominate the nature of the wholeair supply to give the result as herein described from the radialfeeding of air jets. The electrodes 15 and nozzle l2 may be adjustedfrom the positions shown and placedas a group at any desired positionalong the axis of chamber B. This is done by making slipping fits in themember support l3 for these parts.

Referring to clutch 6, suitable arrangements for it are indicated inFigs. 4 and 5. The motor slots of hubl9 as indicated. The hub can beeasily assembled on and taken off shaft I! by the means described and apositive shaft drive for the hub is provided. The hub at its right sideis fastened to the frame of fan 2, see Figs. 2 and 4. Thus the fan ispositively driven and always turns high speed. The clutch can beadjusted for such a .has an opening connected to discharge conduit H,see Fig. 2. The pump has a. casting 30, as is usually provided withneeded pump passages. The pressure regulating means or valve is mountedin this casting as in Fig. 7. Since the structure per se is generallyknown, it will ,be only very briefly described here. Outlet through nut29 is normally closed byspring pressed valve 30a. The area of valve 30ais subject to the pump discharge pressure from passage 3|. does notopen, being spring closed, until the pressure on its area. is sufficientto overcome the spring. When opened the action is to by-pass throughsuitable passages. enough of the pump The valve discharge to keep thepressure constant. "The by-pass is through openings 32 and 33, when theyregister. to conduit 34. The latter connects to the suction side of thepump. The one by-pass indicated is merely by way oi example. There maybe others.

It will be clear that the quantity of oil bypassed is determined by thedegree of pressure necessary to move the valve far enough against itsspring to cause passages 32 and 33 to register more or less. Thus thedischarge pressure is easily regulated by regulating the spring load onthe valve. This is done by compressing spring 35 more or less by turningadjusting screw 36 one way or the other. Nut 31 is a sealing cap for theadjusting screw head. when adjusted the spring controlled by-pass deviceacts to automatically maintain the oil pressure of oil passing throughnut at, constant. The pump is generally slightly oversize. When itstarts to operate,

the burnerfeeding oil pressure is established 1 practically at the sametime as the pump starts.

The tendency is toward excess pressure. This excess is prevented bytheby-pass action. And the oil is delivered with an atomizing nozzlepressure easily determined between wide limits by hand adjusting of theby-pass valve device. The description of one such device is given withthe idea of merely illustrating the well-known principles involved inadjusting the oil pressure discharge from the pump as a separate elementper se, of the combination.

A conventional atomizing nozzle in considerably more than full size isshown in Fig. 6. Assume that this one has a rate of one gallon an hour,in which case' the oil pressure under con ventional practice would bearound one hundred 39. Then it feeds through small slots W in saidsurface. These are generally tangent to the upper circle of surface 35.They release the oil into the cone-shaped space above. This has anorifice M. It is around one hundredth of an inch in diameter. The actionis for the oil from slots Mi to spin in the space to which it isreleased. The oil pressure is converted largely to oil velocity. Thetangent direction causes the spinning. The restricted orifice does notstop the spinning but it acts to center the stream in an extremely smallthread-like whirling mass. The further release of the .pressure from theoil in this stream as it expands beyond the orifice makes a secondconversion of pressure to velocity. The angle of the opening above theorifice will give the action in a spray angle wanted in the burner.Reference to the aforesaid published article will show how much thisnozzle art per se, is attended to up to a very recent time. The

practice has been and it has been much emphasized, to have oil burnersget the most emcient attainable form or atomized spray. The nozzles areusually marked individually by their rate per hour of oil discharge whenused at high enough pressure for their best eflici'ency. The user or hisinstalling agent understands what this high pressure is to be if thenomlesare not actually marked to indicate the oil pressure with whichthe nozzle is intended under prior practice to be used for suchefdciency. Of course as the pounds per square inch. Its action is foroil to feed along passage 38 to irusto-conical surface B, is ignited byspark gap indicated. The flame published article shows, the rate isafiected by viscosity of oil, which depends on the oil grade, andtemperature. The general principle is to adiustevesoastousethenonletoget the most eflicient spray atthemarked ra'teof oil consumption.

According to one of the ideas in my invention use is where under theprior art practice referred to, a nozzle size small enough totheoretically get the low burning rate wanted for a particular use suchas heating hot water, would give too much 'nozzle trouble under generalprior art burner practice.

Referring to my example; I will explain the principles involved in thestructure and mode of operation. In Fig. 1, a conventional nomle i2 suchas shown in Fig. 6 by way of example, sized for a one gallon rateaccording to prior practice can be used with advantage in my combinationfor a muchlower oil consumption rate Thestructure shown will accomplishmy main purpose. The mode oi operation with the size of atomizing nozzlealready given for the example, is as follows: The motor is switched onand ofl by the usual means. When it starts, the fan always starts theairstream at about the same instant, but the oil pump is idle in thebeginning. After the air stream is fully underway, the oil pump isstarted and the atomizing nozzle starts spraying at practically the sameinstant. The clutch element d causes this timed relation of air and oilfeed. The delayed oil spray starts from the rear portion or someintermediate portion along the axis of the space E, Fig. l. The air isforced in jets, from space A, into space B at all radial angles andmeets the oil spray for mixing. The mixture, or carburetted air in spaceis made and the air and oil of the mixture for the flame support,continues to be supplied in the fashion described. The flame will startin the space E as the air fed is radially pressed in toward the axis ofthis space. This holds the flame in a compact mass form for burningmixture.

The conditions are all specially provided with the purpose of receivingthe oil spray in such a way as to maintain a satisfactory fire eventhough the atomizing nozzle per se is working substantially below itsknown eillciency as a spray producing device. The nozzle size isdeliberately chosen and the oil pressure to feed it from the pump isdeliberately chosen, in the example given at about twenty-five poundsper square inch, so

that the'efiiciency of the spray per se is substantially less thannormal. The normal pressure in prior art practice is about one hundredpounds per square inch for full spray emciency. This change is made fromone hundredto twenty-five pounds pressure to get a lower volume of oildelivered to the flame during the time of burning and in lieu of meetingthe troubles of a smaller nozzle orifice worked with much higherpressure to give commonly sought nozzle spray eiilciency, the change ofpressure now being arranged to give the low volume of oil in the sametime with less than full spray efiiciency. My structural armorepractical nozzle size, i. e. an inexpensive one and large enough toavoid the clogging tendencies or smaller ones. The result is that itbecomes practical to operate a gun type burner at 'a rate of aboutone-halfgallon per hour in oil burners are advertised with nozzles ratedlower than one gallon per hour but they are not used much on account ofthe nozzle troubles referred to and the tendency in actual use is toavoid nozzles less than the one gallon ratio as I have stated.

With any nozzle construction, as the orifice size is decreased, and thusthe oil spray volume is decreased, so far as it is practical size nozzleaccording to any prior practice it can'be used by my combination at alower rate. For example attends the attempt to get a corresponding lowrate of oil consumption well below one gallon an hour bymerely'proportioning the nozzle orithe specific nozzle size I havereferred to is one v rated at one gallon an hour. With that one I havereduced the oil rate to about a half gallon an hour. According to thesame principles, when a practical nozzle appears for satisfactory use inprior art gun type burners, I can use that smaller one and yet continueto get a substantially smaller rate as compared to the prior artpractice or mode of operation.

The apparatus shown in Fig. 1 will work with the nozzle and its ignitionterminals positioned further to the left than the position shown. Iprefer-now to have a position far enough back of the forward end ofcylinder 3 to have the flame start well within space E for this reason.The flame then begins as a flame in a retort. It is at least partiallywithin the space B. When this is so the radially directed air jets actonthat portion of the flame. to condense it somewhat. I believe that theflame emerges from the front endof space B surrounded by an envelope ofair which goes out with the flame. The preferred way of running is witha part of the flame burning well within space B as a retort and part ofit burning outside as an extension of the flame inside such space.

With regard to the closures at the front end .of space A and the rearend of space B there is no objection to providing openings through theseclosures but they should not be large enough to spoil the eflect of theradial openings through cylinder M. The radial supply of air throughthis cylinder is a most desirable feature of the combination.

The combination in one aspect is arranged for efllciency of the priorart atomizing nozzle. But by doing that the rateof oil consumption issubfat flce in the prior burner constructions for such a rate.

Having disclosed my invention 1 claim: 1. In an oil pressure atomizingburner of the kind having an oil pressure atomizing nozzle, ad

jacent ignition means, power mechanism to pump the oil through thenozzle at a predetermined constant pressure, a fan to supply air, meansto hold back the oil supply automatically unless the air supply fan isin substantially full operation,

an air tube to direct air from the supply fan to meet the oil adjacentthe nozzle, the combination of a tubular cylinder, provided with manyperforations closely spaced both circumferentially and axially andgenerally distributed over substantially the whole cylindrical surface,said cylinder being positioned inside and spaced from the air tube toform a jacket, the jacket being connected to the fan, for receivingsubstantially all of the air supply to be directed through the cylinderperforations in many small pressure jets, said nozzle being positionedaxially to discharge directly into the rear portion and generallylengthwise of the cylinder across such jets, the perforated part of saidcylinder extending from the place of oil discharge and far enough insidethe air tube to substantially complete oil and air mixture inside thecylinder for both starting and continuing a substantial part of the fuelcombustion in said cylinder before the mixture leaves the cylinder.

2. In an oil pressure atomizing burner of the type having an oilpressure atomizing nozzle with an orifice of a size to deliver at therate of about one gallon an hour when the oil pressure is the apparentlyfoolish purpose of decreasing the I stantially lowered. Thiseifect'alone would not be useful if the'result were to substantially decrease the efllciency of the burner. Such result does not follow,however, because the structure and mode of operation prevents it. Theactual result is a good heating flame at the low rate of oil consumptionin the gun type burner. And the oversize nozzle used avoids all thetrouble which around one hundred pounds per square inch, an air supplyfan, an air tube to direct the air from said fan to the oil, mechanismto pump the oil through the nozzle at a predetermined constant pressurewhich is adjustable, and means to hold back the. oil supplyautomatically whenever the air supply fan is not running atsubstantially full speed,- the combination of a tubular cylinderprovided with many perforations closely spaced both circumferentiallyand axially and generally distributed over substantially the wholecylindrical surface, said cylinder being positioned inside and spacedfrom the air tube to form a jacket for receiving substantially all ofthe air around the cylinder, said jacket being adapted to direct the airthrough the cylinder perforations in many jets,- said oil nozzlebeingpositioned to discharge directly into the rear portion andgenerally lengthwise of the cylinder across such jets, the

perforated part of said cylinder extending from.

the region of oil discharge and forwardly far enough to substantiallycomplete oil and air mixture inside the cylinder,-sald burnercombination being adapted to operate satisfactorily at an oilconsumption rate substantially as low as onehalf gallon an hour whensaid mechanism is adjusted to provide an oil atomizing pressure as f lowas about twenty-five pounds per square inch.

' JOSEPH a. mom.

